1. Technical Field
The present invention relates to a semiconductor device and a manufacturing method.
2 Related Art
In the field of renewable energy such as solar power and wind power, the field of automobiles such as hybrid automobiles and electric automobiles, and any field that demands efficient power conversion such as trains, power semiconductor devices (referred to hereinafter simply as semiconductor devices) are widely used. A next-generation semiconductor element such as a silicon carbide (SiC) compound semiconductor element is mounted in such a semiconductor device. For example, Patent Document 1 discloses a semiconductor device in which an SiC diode is reversely connected in parallel with a silicon (Si) semiconductor switch. An SiC compound semiconductor element has a high withstand voltage because the insulated breakdown electrical field strength is higher than that of a conventional Si semiconductor element, and it is possible to realize a miniature semiconductor device that is capable of operating with high efficiency and at high speed because this SiC compound semiconductor element has a higher impurity concentration and a thinner active layer than a conventional Si semiconductor element.
Patent Document 1: Japanese Patent Application Publication No. 2004-95670
However, although it is possible for the SiC compound semiconductor element to withstand being used at high temperatures, there is a problem that the reliability of the semiconductor device drops due to degradation of the wire bonding portions and the electrode films when the chip junction temperature increases.
Although a large current capacity is desired for a semiconductor device, it is impossible to make an SiC compound semiconductor element as large as an Si semiconductor element due to insufficient crystal quality, and therefore an electrical field relaxing region (also referred to as a guard ring) provided in the circumferential edge of the semiconductor element must be designed to be thin. Here, due to a strong electrical field being focused on the guard ring, insulation breakdown can occur at the interface between the semiconductor element and the gel filler material used to seal the semiconductor element.